Mechanical ore-roasting and like furnace.



J. HARRIS.

MECHANICAL ORE ROASTING AND LIKE FURNACE.

APPLICATION FILED NOV. 17. 1911.

1,149,754. Patented Aug. 10, 1915.

COLUMBIA Pm. CO" WASHINGTON. II. C.

JOHN HARRIS, or SHEFFIELD, ENGLAND.

"MECHANICAL 'onn nons'rme A ND LIKE FURNACE.

Specification of Letters Patent.

Patented. Au :10, 1915.

Application filed November 17, 1911. SerialNo. 660,844.

To all whom it may concern Be it known that 1, JOHN HARRIS, a subject ofthe King of England, residing in Shefiield, in the county of York,England, have invented certain new and useful Improvements in orRelating to Mechanical Ore-Roasting and like Furnaces, of whichthefollowing is a specification.

This invention relates to mechanical ore roasting and'like furnaces foruse in the generation of gases for the production of fluid acid itsobject being to prevent the creation of dust within the furnace and toobtain'an increased purity and clarity in raw acid produced fromthefurnace gases.

It iswell known that dust arising within the furnace iscarried alongwith the gases evolved therein -and isthe cause of part of the impurityand of nearly the whole of the discoloration in the raw acid. Variousattempts have been made to solve this dust problem but they have notsucceeded to any appreciable degree in reducing the discolorationand-increasing the purity of the raw acidbecau'se they have beendirected to the symptoms instead ofto the causes of the trouble.

'I have" found that the greaterpart if not the whole 'of the dustcausingthe discolorationandconsequent impurity of the acid is.

thatwhich arises from that portion of'the ore or other material beingroasted which-is yet in acom-parati ely cold condition and the mainfeature of the present invention consists in so treating the charges ofore or like material during the initial stagesof the roasting operationthat dust pollution of the gases supplied to the acidproducingprocess iseliminated during such initial stages. In thepreferred method ofeffecting this the material is fed to the furnace intermittently andeach batch is wholly removed fromthe delivery area before the nextarrives and is then so manipulated that it travels gradually anduniformly along a'predetermi'ned p ath' in such manner that partiallyheated portions are'not'moved back to mix with colderp0rtions, and thelatter do not overtakeand'mixwith parts at a higher temperature, for'lhave found that one of the'most fruitful sources of the noxious dustisthe promiscuous mixing of material-at diiferent temperatures, whetherthe mixing is 'eifected by feeding the material upon that already in thefurnace or whether it takes place subsequent to delivery while thematerial is'still at a temperature substantiallybelow that of itssurroundings. The extent of this manipulation will depend upon thenatureof the material being roasted, but generally it is advisable to continueit until the material reaches approximately the temperature of itssurroundings. Beyond this point any desiredmeans for manipulating thematerial maybe employed. v Additional devices-tending to reduce theformation of dust may also be employed if desired, such as'theemployment of sealed discharges, seals around.

the rabble'shaft and by so arranging the gas apertures in relation tothe ore openings that the ore does not drop intheIpath ofthe draftthrough the furnace.

The-accompa-nving drawi gs are diagrammatic of the preferred method ofcarrying out this invention, Figure lfrepresenting a sectionalelevation-of a-furnace and-Fig. 2 a

sectional plan of the first hearth, o the line i The" furnace showncomprises three superimposed roasting 'ehambersA, A and A? and the 'oreor,-.other material to be' roasted is fed intermittently through thefeed opening B to the uppermost chamber A -by' any desired meanssuchas'rabble arms A working upon the roof of the furnace. Each batch ofmaterial is then moved gradually anduniformly forward along the desiredpath'by inclined rakes-C C on the rabble arm D carried by the shaft Eadjacent to which the material falls. It' is desirable-for each batchofmaterial to be spread also completely around; the shaft E, else aportion of the hearth of the chamber will not be utilized. For thispurpose the first inclined rake C acting upon eachbatch of material isofsuch-len'gth and inclination having regard to the quantity 7 ofmaterial in each bat'c'h' that the latter is spreadcompletely ing Bbythe inclined rake C and that the a next batch Will be fed upon a clearspace out of contact with ore or like material at a higher temperature.When the inclined rake C reaches a newely delivered batch the previousbatch has been moved if not en tirely beyond the area traversed by thisrake at any rate so far from the shaft that the new batch is not mixedtherewith. Simi larly each of the inclined rakes C leaves a clear spacebehind it upon which material is moved by the adjacent rake on the shaftside, and so there is no harmful mixing of material at differenttemperatures.

The path of the outer edge of each of the inclined rakes (l coincideswith or overlaps thatof the adjacent inner edge of the next rake inorder to insure that all the ore displaced by one rake comes under theaction of the next one and is not left be tween them to mix with thatmoved by the first rake at the following revolution.

v It willbe understood that, as is the generalpra'ctice in this class offurnace, the floors of the chambers A, A and A are lined with powderedanthracite, coke or the like. The lining will also form a circular wallaround the shaft E co-inciding with the path of the outside edge of theoutermost rake carried by the arm D except where this path'is overlappedby that of the arm D as shown in Fig. 2. Hence the ore coming under theaction of the outermost rake C on the arm D will be limited in itsradial movement by this wall which, co-acting with the said outermostrake, will enable the latter to carry the ore around the shaft and todeliver it to the area traversed by the arm D whence it will be moved bythe rakes on the arm D The area traversed by the inclined rake Cispreferably raised above the bed of the chamber A in order to decreasethe length of fall of material being fed to the furnace and to preventthe possibility of material which has left this inclined rake movingbackward to mix with a newly delivered batch. This raised table G may besimply formedwith the powdered anthracite, coke or the like which thefloors of the chambers are lined by arranging the lower edge of theinclined rake C at the requisite distance above thefloor of the chamber.When feeding this lining substance through the furnace initially it willof course fill in the space below the rakes.

' The second rabble arm D which acts upon the ore or like material .Willbe provided with inclined rakes C, with plow rakes F or the like or withboth according to the substance being treated and its temperature whenit reaches the area traversed by this arm.

The gases evolved in the furnace are led tothefacid producing process bythe flue A other method of manipulating the material during the initialstages of the roasting operation so as to feed it gradually anduniformly forward and to keep portions thereof which are at differenttemperatures from promiscuous admixture may be employed withoutdeparting from this invention, and there may be combined therewithadditional devices tending to reduce the formation of dust within thefurnace. For example, the discharge of the furnace may be sealed bycontinuing the casing H of the conveyer J substantially beyond the endof the conveyer, thus causing the material to fill completely thisextension of the casing before any portion arrives at the outlet H Sealsmay also be provided in the feed apertures, B, B and B as indicated bythe inclined plates B therein, and around the rabble shafts. Such lastmentioned seals may be formed by annular plates K surrounding the shaftsE and covering the openings in the roasting chamber floors through whichthe shaft passes. The plates are preferably loose so as to allow ofrelative movement between the shafts and floors and to prevent damage byany solid body which may accidentally be situated in the path of therabble arms. In combination with each of these annular plates K anadvanced plow, indicated at L, is carried by the rabble arm to move anymaterial being roasted away. from the shaft openings in the archedfloors and to direct it under the action of the adjacent rabble rakes.

A. further arrangement preventing the formation of dust is to disposethe gas apertures Min relation to the feed openings B, B and B so thatthe oredoes not drop in the path of the draft through the furnace. Thismay be effected by arranging the gas apertures M at the corners and thefeed openings in the center line of the furnace as shown clearly in Fig.2. Both may, however, be centrally disposed as indicated in the archedfloor of the chamber A and in this case the feed opening is situated onthat side only of the gas aperture which is opposite to the directionfrom which the draft through the furnace comes.

What I claim and desire to secure by Letters Patent is 1. The hereindescribed method of treating ore in a roasting furnace comprisingintermittently feeding charges of ore to the furnace and moving thedifferent batches over the hearth surface therein in such manner thatthe successive charges are maintained separate throughout the process,whereby mixing of charges having different temperaturesis prevented, forthe purpose described. I

2. The herein described method of treating ore in a roasting furnacecomprising intermittentlyfeeding charges of ore'to the furnace andmoving the different batches across each of a plurality of hearths andfrom one hearth to another in such manner that each charge is removedfrom the delivery area of a hearth prior to the delivery thereon of afollowing charge, whereby a plurality of successive charges aremaintained separate on said initial hearth and throughout the roastingprocess until they have reached substantially the same temperature, forthe purpose described.

3. The herein described method of preventing the formation of dust inthe operation of roasting ore in a furnace wherein the ore is moved overa hearth by rabbles on a rotating shaft, compnsing intermit- Gopies ofthis patent may be obtained for five cents each, by addressing thetently feeding ore onto the hearth adjacent the shaft, the amount ofeach charge being limited to that which can be displaced at a revolutionof the shaft, whereby the delivery area of the hearth will be cleared ofeachcharge before another charge is deposited thereon, and maintainingthe successive charges separate while they differ materially intemperature.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

JOHN HARRIS.

Witnesses:

ARTHUR H. GREENWOOD, LUTHER J. PARK.

Commissioner of Patents.

Washington, D. 0

